I've been contemplating this for a while, as I've been needing a portable metronome which doesn't sound as annoying as the one built into REAPER. I have no grudge with it, really, but my wife is really bugged by it. She says it reminds her of the sound the Octopus from Disney's Peter Pan made when walking, and, although I've never heard how that sounds, I must admit there just might be a resemblance.
Of course, I could easily do this with an ATtiny2313, and maybe even cram some basic audio BPM detection into it. Would be cheaper, too - that's a major concern for me. But there's something compelling in building stuff only out of logic ICs. So why not build a metronome with a display only out of 4000 series chips? I'm not really sure about how it would work, but I'm pretty certain about some would-be problems.
1. Input - I don't think a PC keyboard-like repeat action would be easy to implement, so that leaves me with a bunch of switches like +1bpm, +10bpm, +100bpm, etc. - unless I figure out how to interface a rotary encoder with CMOS logic, and I don't have a model of one in my simulation software, either. Can anyone send a Proteus model of an encoder my way?
2. Tap tempo - this depends on how the metronome would actually be implemented. Maybe would be feasible, maybe not.
3. Time signatures - of course, this is a problem only if it actually plays different sounds on different beats.
more to come...
Any ideas?